Apparatus for submarine signaling



Dec. 12, 1944. w 2,364,679

PPARATUS FOR SUBMARINE SIGNALING Filed 0013. 8, 1941 Dec IZ, 1944.

2 She ets-Sheet 2 R L WILLIAMS APPARATUS FOR SUBMARINE SIGNALINQ -FiledOct. 8, 1941 'INVENTO'R Patented n... 12, 1944 APPARATUS FOR SUBMARJNESIGNALING Robert Longfellow Williams, Newton, Masa, as-

signor to Submarine Signal Company, Boston, Mama, a corporation of MaineApplication October 8, 1941, Serial No. 414,122

4Claims.

The present invention relates to underwater sound producing devices.More particularly the present invention relates 'to electromagneticimpact-operated underwater sound transmitters.

The present invention is intended to provide a device for producing anunderwater sound or noise of more or less continuous nature butcontaining a large frequency spectrum while at the same time having aconsiderable energy content. Such a device has particular use as a soundsource for tripping acoustically operated mines,

particularly those of unknown frequency, as well as a sound source to beused for the calibration of binaural direction finding systems.

The invention will best be understood from the following descriptiontaken in connection with the accompanying drawings in which Fig. 1 showsa vertical section through my sound producer or oscillator as it will behereinafter called; Fig. 2 shows a horizontal section taken along theline 2-2 inFig. 1; Fig. 3 shows a plan view of the armature of theoscillator; and Fig. 4 shows a vertical sectlonof a modification of theoscillator.

C Referringto Figs; 1 and 2, a cylindrical steel forging I forms thebody of the oscillator and with diaphragm members 2 and 3 havinginwardly flanged rims 2a and 3a, respectively, by which the diaphragmtnembers are fastened on either side of the member I by the bolts 4,with the interposition of gaskets 28, 21, thereby pro-' shaped andhaving integrally formed at its center a striker 9 which is in the formof a solid cylinder terminating below the armature 8 in a hammerheadshaped boss ID. A plan view of the armature is shown in Fi 3. It will beobserved that the arms of the cross-shaped armature are slotted as at 30to reduce eddy currents. Guide pins 3| are provided which are positionedto fit into the corners at the junction of the arms of the cross of thearmature 8 and thereby prevent the armature from rotating with respectto the electromagnet field member 5.

The striker 9 is held in position by a hollow cylindrical guide memberII which is threaded into a central aperture in the member I by thethreads I2 and locked in position by nut 24. The guide member II has acylindrical recess I3 within which is positioned a spiral spring I4whose lower end bears against a shoulder I5 on the striker 9. Since thestriker 9 and the armature 8 are firmly united in one piece, the springIt will thus urge the boss end III of the striker against the diaphragm3 and the armature away from the magnet field. The striker is made ofsuch a length that its upper end will then be spaced away from the upperdiaphragm 2 by a distance equal to the desired stroke which may varywith the frequency and the noise characteristics desired. The strokemay, for example, be of the order of 0.06 inch.

It will be observed that the tension of the spring It can be regulatedby adjusting the guide member I I. The spring tension is preferablyadjusted so that the vibrating system formed by the spring It and themass of the striker and armature will have a resonant frequency at twicethe frequency of the alternating current exciting the winding I.

In the operationof the device when the flux I in the field magnet 5reaches a maximum value, the armature 8 will be attracted toward thefield 5, drawing the striker 9 upward against the action of the springI4 and striking a blow against the diaphragm 2. When the current throughthe coil I and hence the flux in the magnet 5 falls to zero, the springIt will urge the striker downwards, thereby striking a blow against thediaphragm 8. The action will then be repeated. Since the alternatingcurrent will reach a maximum value twice in each cycle, there will be120 oscillations of the striker 9 per second with cycle excitation ofthe coil 5, and'for each oscillation both of the diaphragms 2 and 3 willalternately be struck once. In place of alternating current, the magnetmay be energized with direct current which is periodically interruptedwhen the striker makes contact with the upper diaphragm. The diaphragmmembers 2 and 3 are preferably thickened at the center and may be tunedto any desired frequency preferably in the lower audible range and to afrequency different from the striker freqeuncy. However, greater outputat specific frequencies can be obtained by tuning the diaphragms to afrequency which is a multiple of the frequency; of oscillation of thestriker. By this arrangement a relatively large amount of sound energycan be radiated into the water.

. center of the bridge 26 there is threaded a stop 22 which can belocked in, any desired position by a locking ring 23. For maximumamplitudthe stop 22 is positioned so that the striker 9 will just makecontact with it before the armature ii strikes the magnet field wherebythe armature is prevented from sticking to the field member. As in thepreceding modification, the resonant frequency of the oscillatingstriker can be adjusted toequal the frequency of magnet pull, e'. g,twice the frequency of the alternating current supplied to the magnet,by varying the position of member M. In. this modification it may besimpler to introduce the field supply cable ll through a stuffing plugmounted in the cover member it instead of in the manner shown in Figs. 1and 2.

Having now described my invention, I claim:

1. A submarine signaling device comprising a watertight casing formed ofa pair of axially aligned juxtaposed cylindrical memberssecured togetherand having heavy rim portions and thinner central portions, defining acavity within said casing, one of said members being adapted to act as'an underwater sound radiating diaphragm adapted by one face to contactthe water, the second of said members having a central aperture,electromagnet poles secured to said second member within said cavity andsurrounding said aperture, a striker mounted for axial oscillationwithin said aperture and adapted to strike said diaphragm, an armaturecarriedby said striker adapted to be attracted by said magnet, springmeans tending to urge said striker against said diaphragmand saidarmature away from said magnet, coil means adapted to be energized byalternatingccurrent for exciting said magnet and means forming awatertight cover over the back side of said second member.

2. A submarine signaling device comprising av Watertight casing formedof a pair of axially alignedjuxtaposed cylindrical members securedtogether and having heavy rim portions and thinner central portions,defining a cavity within said casing, one of said members being adaptedto act as an underwater sound radiating diaphragm adapted by one face tocontact the water, 'the second of said members having a centralaperture, electromagnet poles secured to said second member within saidcavity and surrounding said aperture, a striker mounted for axialoscillation within said aperture and adapted'to strike said diaphragm,an armature carried by said striker adapted to be attracted by saidmagnet, spring means tending to urge said striker against said diaphragmand said armature away from said magnet, coil means adapted to beenergized by alternating current for exciting said magnet, means forminga watertight cover over the back siilebfsaid second member and meansformed within said cover for limting thestroke of said striker in itstravel away from said diaphragm.

3. A submarine signaling device comprising a cylindrical mass memberhaving a central aperture, a pair of'similar underwater sound radiatingdiaphragms having inwardly flanged rims, one diaphragm being secured byits flanged'rim to each side of said mass member, thereby forming ahollow watertight casing, an oscillatable striker mounted for axialoscillation in said aperture so as to strike each diaphragm alternately,spring means tensiom'ng saidstriker against one of said diaphragms,alternating current energized electromagnet means mounted on said massmember and an armature carried by said striker adapted to be attractedby said electromagnet for compressing said spring and forcing saidstriker against the other of said diaphragms.

4. A submarine signaling device comprising a cylindrical mass memberhaving a central aper ture, a pair of similar underwater sound radiatingdiaphragms having inwardly flanged rims, one diaphragm being secured byits flanged rim toeach side of said mass member, thereby form'- ing ahollow watertight casing, an oscillatable striker mounted for axialoscillation in said aperture so as to strike each diaphragm alternately,spring means tensioning said striker against one of said diaphragms,alternating current energized electromagnet means mounted on said massmember and an armature carried by said striker adapted to be attractedby said electromagnet for compressing said spring and forcing saidstriker against the other of said diaphragms, the stiffness of saidspring being proportioned with regard to the combined mass of saidstriker and armature to produce'a resonant oscillatory system having aresonant frequency twice that of the magnet-energizing alternatingcurrent, said diaphragms being tuned to different multiples of saidresonant frequency.

ROBERT LON GFELLOW WILLIAMS.

